1. Field of the Invention
The present invention relates to a charged particle beam apparatus, a charged particle beam control method, a substrate inspection method and a method of manufacturing a semiconductor device.
2. Related Background Art
Heretofore, for a deflector used in a charged particle beam apparatus, for example, an electrostatic deflector, a quadruple or octal deflector has been generally used which comprises four or eight electrodes arranged to surround an optical axis, and positive and negative voltages are applied to the electrodes facing across the optical axis to produce an electrostatic field which controls a charged particle beam. This will be specifically described with reference to the drawings.
FIGS. 9A to 9D are sectional views showing an electrostatic deflector described in T. H. P. Chang et al, Multiple electron-beam lithography, Microelectron. Eng. 57-58 (2001) 117-135. FIG. 9A is a sectional view of a quadruple deflector 820 comprising four fan-shaped flat electrodes EL820a to EL820d, which is cut along a plane perpendicular to an optical axis Ax, and FIG. 9B is a sectional view of the deflector 820 along an X axis of FIG. 9A. Further, FIG. 9C is a sectional view of an octal deflector 822 comprising eight fan-shaped electrodes EL822a to EL822h, which is cut along a plane perpendicular to an optical axis Ax, and FIG. 9D is a sectional view of the deflector 822 along an X axis of FIG. 9C.
Describing, for example, the octal deflector 822 shown in FIG. 9C, for deflection in a forward direction (arrow direction) on the X axis, a voltage of (√2−1) V is applied to the electrode EL822a, V to the electrode EL822b, V to the electrode EL822c, (√2−1) V to the electrode EL822d, −(√2−1) V to the electrode EL822e, −V to the electrode EL822f, −V to the electrode EL822g, and −(√2−1) V to the electrode EL822h, so that a tertiary term of the electrostatic deflection field disappears to allow for a wider uniform electric field area. This enables beam deflection with significantly reduced deflection aberration.
Also, a proposal has been made to improve optical performance in an electron beam lithography apparatus using the deflectors shown in FIGS. 9A to 9D. FIG. 10 is a partial configuration diagram showing an electron beam lithography apparatus described in Japanese laid open (kokai) No. 2001-283760. In an electron beam irradiation device 900 shown in FIG. 10, an electrostatic main deflector 952 is disposed in a magnetic field of a magnetic objective lens 954, and a pre-deflector 950 is disposed on an object surface side of the objective lens 954 while a post-deflector 953 is disposed on an image surface side of the objective lens 954. The electron beam irradiation device 900 shown in FIG. 10 is used in the electron beam lithography apparatus, and widely deflects an electron beam EB on a wafer W which is a sample, in order for a faster lithography process. Therefore, a deflection system is optimized in such a manner that deflecting voltages are lowered by maintaining high deflection sensitivity and that coma aberration and an incidence angle of the electron beam EB on the wafer W will be 0. The optimization of the deflection system in the device of FIG. 10 is implemented in accordance with locations of a plurality of deflectors on the optical axis, a voltage ratio among the deflectors, and phase setting.
However, if an attempt is made to further increase the resolution of the electron beam irradiation device 900 shown in FIG. 10 or to increase the amount of deflection of the electron beam EB, more deflectors are arranged inside, in front of and in the rear of the objective lens 954, thus increasing the number of components and wires on the periphery of a pole piece of the objective lens 954. This increases the burden on mechanical assembly, and makes it difficult to produce a higher vacuum on the periphery of the pole piece due to an increase of exhaust resistance. Another problem is an increase in the number of power sources due to the increase in the number of deflectors. On the other hand, there is a limit to the actual number of deflectors and to arrangement space, which does not allow for optimal locations on a physical design, thus making it difficult to further improve performance.